Clinging to submerged debris in shallow marine mangrove forests in the French Caribbean, thread-like microorganisms — perfectly visible to the naked eye — have earned the title of largest bacteria ever known.
At about one centimeter in length, they are roughly the size and shape of a human eyelash, beating the competition by about 5,000 times the size of the garden’s diverse bacteria and 50 times the size of the bacteria once considered giant. In human terms, this is like seeing a person as tall as Mount Everest.
Prokaryotes were discovered by Olivier Gross, a biologist at the University of the Antilles in 2009, and observed that they swung gently in sulfur-rich waters among the mangroves of the Guadeloupe archipelago. Gross said in a press briefing that the bacteria clung to the leaves, branches, shells of oysters and bottles that sank in the tropical swamp.
He and his colleagues initially thought they might be complex eukaryotes or perhaps a series of related organisms. But years of genetic and molecular research have revealed that each streak is, in fact, a towering bacterial cell, genetically related to other sulfur-oxidizing bacteria. “Of course, that was a huge surprise,” Jean-Marie Voland, a microbiologist at the Joint Genome Institute in Berkeley, California, said at the press conference.
Gross and his colleagues posted this week An article in Science that explains everything they’ve learned About the formidable new bacteria, which they named Candidatus (California) Thiomargarita Magnifica.
Their findings expand our understanding of microbial diversity in ways microbiologists never thought possible. Scientists previously hypothesized that the size of bacteria would be limited by several factors, including a lack of intracellular transport systems, a dependence on inefficient chemical diffusion, and the surface-to-volume ratio needed to meet energy needs. However, the size of one California. T. Magnifica The cell is at least twice an order of magnitude higher than the expected maximum that the bacteria could theoretically achieve, Volland said.
Voland, Gross, and colleagues are still learning how — and exactly why —California. T. Magnifica Manages its sheer size. But, so far, it’s clear that California. T. Magnifica It oxidizes hydrogen sulfide from its sulfur-rich environment and reduces nitrates. About 75 percent of the cell’s volume is a bag of stored nitrate. The cyst crushes against the cell envelope, limiting the depth at which nutrients and other molecules need to diffuse.
While bacteria tend to have floating DNA, California. T. Magnifica It appears to have more than half a million copies of its genome grouped into several membrane-bound compartments that the researchers named pipiens, after the tiny seeds in the fruit. The distribution of pepinates across the outer edges of the bacteria could allow local protein production, eliminating the need to transport proteins over long distances.
The next step in studying these giant bacteria is for scientists to figure out how to grow them in laboratories. Currently, researchers collect new samples from the mangrove forests every time they run out. But, this was tricky as they seem to have an ambiguous or seasonal life cycle. For the past two months, Gros hasn’t been able to find any. “I don’t know where they are,” he said.
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